A conventional angle-adjustable joint shown in FIG. 5 used in a collapsible chair has a male joint 11, a female joint 12 and a bolt 13 combined both joints together. This conventional angle-adjustable joint is found to have following disadvantages.
1. Its angle adjustability is limited for 90 in the horizontal and the vertical direction.
2. It can only be secured at two kinds of positions adjustable, not able to be secured at any angle between the two positions.
3. In adjusting process, a user may not have enough force to sustain the weight of the thing to be adjusted in its angle.
4. A variety of different sized joints have to be prepared for different things, for lack of common features.